1. The Field of the Invention
The present invention relates to natural pozzolanic materials having reduced-size particles.
2. The Relevant Technology
A pozzolan is a material which, when combined with calcium hydroxide, exhibits cementitious properties. Because of its properties, pozzolans are commonly used as an admixture to Portland cement concrete mixtures to increase the long-term strength and other material properties of these concrete mixtures. In particular, when added to concrete, pozzolanic materials can improve the compressive strength, bond strength, abrasion resistance and other properties of the concrete.
Pozzolans can be either natural or man made. However man-made pozzolanic materials, such as silica fume, fly ash, and granulated blast furnace slag, can be inferior to natural pozzolans in many ways. When used in cement and concrete mixtures, natural pozzolans can facilitate improved lithification, autogenous healing, reduced permeability and voids, reduced expansion and heat of hydration, reduced creep and cracks, reduced microcracking, increased compressive strength, increased resistance to chloride attack, increased resistance to sulfate attack, reduced alkali-aggregate reaction, increased abrasion resistance, decreased water demand, impeded carbonation, and improved durability as compared to the use of man-made pozzolanic materials.
Natural pozzolans are formed when silica rich magma meets with a large quantity of underground water in a volcano conduit. Under high temperature, steam dissolves into the magma mixing with the dissolved carbon dioxide and sulfur gases. When this magma reaches the earth's surface, it blows off the top of the volcano, releasing gases within the magma, causing an explosion of the magma, which then falls to the ground and cools into small porous rocks to form the natural pozzolan. Once the natural pozzolan is mined and the size of the natural pozzolan particles is reduced, the pozzolanic material can then be used in cement and concrete mixtures. However, current processes of reducing the particle sizes of natural pozzolanic materials may negate and/or limit some of the beneficial effects of natural pozzolans.